function dS = R2bpCartesianModel(~,S,u)
    
    R = S(1:3);
    %[km]Current position vector WRT the central body.
    
    r = norm(R);
    %[km]Current distance from the center of the central body.
    
    dS = zeros(6,1);
    %[]Allocates memory for the differential state vector.
    
    dS(1:3) = S(4:6);
    %[km/s]Current velocity vector WRT the central body.
    
    dS(4:6) = -u * R / r^3;
    %[km/s^2]Current acceleration vector WRT the central body.
    
end
%===================================================================================================